The entire contents of Japanese Patent Application No. 9-119693 filed on May 9, 1997 are incorporated herein by reference.
The present invention relates to a computer system and sound controller and, more particularly, to an improved computer system which can set analog audio circuits included as peripheral circuits of a sound controller in a power down mode in accordance with the state of the sound controller, a sound controller, and a power down control method applied thereto.
In recent years, various laptop or notebook type personal computers have been developed. Such personal computers have various power management functions to attain power savings. As typical power management functions, a suspend function of turning off the power supply for practically all the devices except for the main memory, a CPU sleep function of dropping the operation speed of the CPU in a system idle state, and the like are known.
Some peripheral devices used in a computer system can switch themselves from a normal mode to a power down mode requiring smaller consumption power than in the normal mode. The power down function of such device is normally used in combination with the above-mentioned CPU sleep function or the like. With these functions, the consumption power of the entire system can be reduced.
As a device with the power down function, "OPL3 Single-chip Audio System 3" available from YAMAHA CORPORATION is known. This sound controller is a sound controller chip having functions of FM sound source and CODEC, and is currently the standard sound source mounted on a personal computer.
The sound controller "OPL3" has a control register for switching its operation state between the normal and power down modes. When a sound driver program that controls "OPL3" sets a power down mode flag in the control register, "OPL3" is switched from the normal mode to the power down mode. In this power down mode, power supply to internal circuits for reproducing sound data is stopped, thus attaining power savings. When the sound driver program resets the power down mode flag in the control register, "OPL3" resumes the normal mode from the power down mode.
However, since the power down function of "OPL3" can only set that chip in the power down mode, even when the sound driver program sets the power down mode flag, analog audio circuits such as audio amplifiers serving as peripheral circuits of the sound chip are not set in the power down mode. For this reason, the analog audio circuits keep receiving operation power even during non-reproduction periods of sound data, thus wasting electric power.
The power down function of the sound controller preferably executes dynamic control not only in the system idle state but also in accordance with the presence/absence of sound data reproduction during system operation. However, in the conventional function, the sound driver program sets the power down mode flag in only the system idle state or suspend state, as described above, and cannot dynamically set the sound controller in the power down mode during system operation.
As described above, with the conventional function, only the sound controller itself is set in the power down mode, and power savings of peripheral analog audio circuits are not realized. The sound controller is set in the power down mode only in the system idle state or suspend state, but is kept in the normal mode even during non-reproduction periods of sound data.